Manufacture of carbon dioxide ice



Nov. 29, 1938. DU BOIS EASTMAN 2,138,753

MANUFACTURE OF CARBON DIOXIDE ICE Filed June 15, 1935 da 50/3 [as/man INV TOR Patented Nov. 29, 1 938 I UNl'lED STATES PATENT oFFic MANUFACTURE or CARBON Dioxins res Du Bois Eastman, Port Arthur, Tex, assignor to The Texas Company, New York, N. Y., a corporation of Delaware Application June 15, 1935, Serial No. 26,744

. 3 Claims. (01. 62-121) This invention relates to a method of preparing operation but are constructed to permit the indeclear solidified carbon dioxide. pendent removal of each container or are other- As heretofore marketed CO2 has been congealed wise formed so that the cake of carbon dioxide by permitting the gas to expand into suitable ice may be removed from the container.

5 tanks or other receptacles, the cooling effect of The refrigerating fluid, preferably ethane, is 5 expanding the gas from a higher to a lower presutilized in a closed cycle to prevent loss of refrigsure causing a portion of the CO2 to congealinto erating fluid in normal operation. This cycle inlight flakes similar to snow. These flakes are cludes a compressor Hi receiving the fluid from then compressed and marketed as dry ice. The the conduit H5 at a low pressure, for example,

10 present invention is distinguished from the cuspounds per square inch absolute. The com- 10 tomary procedure by directly freezing liquid CO2 pressor IQ compresses the gas to approximately into a clear solid ice, thus avoiding the complica- 600 pounds per square inch and raises the temtion and heat losses incident to compressing CO2 perature to approximately 200 F. Thefluid is snow, as well as furnishing a more compact then passed through a cooling device illustrated 1.; product. as an atmospheric cooler W for reducing the tem- In carrying out the invention a suitable refrigperature to approximately atmospheric temperaerating fluid capable of being expanded to proture, assumed to be 85 F. The fluid at 600 duce a temperature below the melting point of pounds pressure and 85 F. may then be carried CO2 is employed. A fluid particularly suited for directly to the expansion coils, positioned in :0 this purpose is ethane, which has a vapor pressure the refrigerating unit l2, although it is contem- 20 function, similar to CO2 and which boils at atmosplated to first reduce the temperature further bepheric pressure well below the melting point of for the fluid reaches the expansion coils if desired. CO2. The refrigerating fluid is reduced in pressure'ad- The invention Will be fully understood y jacent the coils 20 from 600 pounds to approxi- 5 erence to the single figureof the drawing wherein mately 10 pounds per square i h This causes there is illustrated more or less diagrammatically a reduction in temperature of the refrigerating a p e pp which y e e p yed fo liquid to a temperature sufiicient to freeze the carrying out the present invention. carbon dioxide liquid in the containers Ill. The The apparatus, as illustrated, includes a comrefrigerating fluid is then carried through the D 4 for receiving 02 and Compressing the heat exchanger 8 wherein it reduces the tempera- 30 S u h one or more stages to a high presture of the incoming CO; to a point well below Sure, 1000 pounds p square nch absolute, for zero so that the pressure on the CO2 may be reexample. This degree of compression will raise duced without vaporizing the same. The 601111- the temperature o the Compressed s t apterflow heat exchanger 8 increases the tempera- 5 proximately 250 F. At this point, being well ture of the refrigerating fiuid'to approximately above the critical temperature'for CO2 (88 F.), 75 F. with little or no reduction in pressure the material will be in the form of vapor. The therein. This gas is then returned to the comcompressed vapor is conducted through a cooler 6 p'ressor i 4 and the cycle is repeated.

, which. maybe an atmospheric cooler or other type Ethane has been found to be a particularly 40 employing an extraneous cooling medium. The useful refrigerating liquid .for freezing carbon 40 compressed gas is reduced in the cooler 6 to a dioxide since its boiling point at various pressures temperature below its critical temperature, for corresponds closely with that of carbon dioxide example, 85 F., whereby the C02 assumes a liquid yet at lower temperatures, sufiicient to freeze the form as it approaches the refrigerating unit. liquid CO2, there exists a substantial temperature 43 The liquefied CO2 is then carried under pressure differential between the ethane and the CO2. At through a. heat exchanger 8 where its temperaa pressure below 40 pounds per square inch ethane ture is materially reduced, a temperature of has a boiling point substantially below that of 56 F., for example, having been found feasible. carbon dioxide at 100 pounds pressure, the difler- The pressure may accordingly be reduced to apential gradually increasing as the pressure is proximately 100 pounds per square inch as the reduced. With a reduction in pressure from 600 50 CO2 passes from the heat exchanger 8 into the pounds to 10 pounds and an initial temperature containers ill of the refrigerating unit [2. The of from 20 to F., a temperature of 120 F. containers III are constructed to accommodate a or lower can be attained from the expanded working pressure of at least pounds. per square ethane, this temperature being well below the 1 inch. They are necessarily sealed during normal freezing point of carbon dioxide. 1

While reference is made herein to specific temperatures and pressures suitable for carrying out the proposed invention, it will be understood that these are illustrative only and that other temperatures and pressures, as well as other refrigerating fluids, may be employed. Any refrigerating fluid having the general physical characteristics of ethane and which will produce a temperature sufiiciently low to freeze the liquid CO2 while the latter is maintained under a liquefying pressure will be satisfactory. Other refrigerating fluids which may be utilized in carrying out the invention are ethylene and ammonia. v

Obviously, many other modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims. I

I claim:

1. The method of freezing liquid carbon dioxide comprising maintaining the same in a liquid state at a relatively low temperature, providing a continuous closed cycle for a normally gaseous fluid of the type of ethane wherein said fluid is compressed, cooled by extraneous means and expanded under low pressure to produce a temperature below the melting point of said liquid carbon dioxide, the expanding fluid and liquid carbon.

dioxide being maintained in heat transfer relation for freezing the latter and passing said cooled expanded fluid in counter-current heat transfer relation to the liquid carbon dioxide before the latter is frozen by the expansion of said fluid.

2. The method of freezing liquid carbon dioxide comprising maintaining a charge of the same in a liquid state in a freezing compartment, compressing a fluid of the type of ethane,'cooling the same by extraneous means and expanding and cooling said ethane in heat conducting relation to said compartment for transferring heat from said carbon dioxide to said fluid, and transferring heat from said liquid carbon dioxide to said fluid as said fluid is exhausted from the vicinity of said freezing compartment and prior to the entrance of the next succeeding charge of said carbon dioxide into said freezing compartment.

liquid state in a chamber, freezing said liquid carbon dioxide in said chamber by the expansion of a fluid of the type of ethane in heat conducting relation to said chamber and pre-cooling said liquid carbon dioxide by passing the same in heat conducting relation to the expanded fluid prior to the entrance of the next succeeding charge of said liquid carbon dioxide into said chamber.

no BOIS EASTMAN. 

